1. Field of the Technology
The present invention relates to control technologies of end-to-end Quality of Service (QoS), and particularly, to a method for ensuring reliability in a network.
2. Background of the Invention
With the continual enlargement of the scale of the Internet, various network services have come into existence and advanced multimedia systems have also emerged in endlessly. A real-time service will be affected greatly if a service, such as the service of File Transfer Protocol (FTP), which is highly burst, or the service of Hypertext Transfer Protocol (HTTP), which contains image files, occurs in networks since the real-time service is relatively sensitive to such network characteristics as transmission delay and delay jitter. Furthermore, as a multimedia service occupies a large amount of bandwidth, it would be difficult to reliably transmit a key service of which the transmission has to be guaranteed in the existing network. As a result, various QoS technologies have been proposed so as to guarantee the reliable transmission of a key service. For example, the Internet Engineering Task Force (IETF) has proposed many service models and mechanisms to meet demands for QoS. At present, what is comparatively approbatory to the industry is to adopt the Integrated Service (Int-Serv) model at the access of a network or at the edge of a network and to adopt the Differentiated Service (Diff-Serv) model at the core of a network.
The Diff-Serv model ensures QoS only by such measures as setting priority. Although the Diff-Serv model has the advantage of high line utilization, it is hard to expect the specific effect of the model. Therefore, the industry introduces a separate bearer control layer and sets up a special Diff-Serv QoS signaling mechanism for the Diff-Serv model of a backbone network, and sets up a resource management layer to manage network topology resources for a Diff-Serv network. The Diff-Serv model using such a resource management method is called the Diff-Serv model including a separate bearer control layer. FIG. 1 is a schematic diagram of the Diff-Serv model. In the figure, 101 is a service server, which belongs to the service control layer and can implement functions including soft-switch, such as Calling Agent (CA); 102 is a bearer network resource manager, which belongs to the bearer control layer; 103 is an Edge Router (ER) and 104 is a Core Router, both of which belong to the bearer network. In the Diff-Serv model, the bearer network resource manager is for configuring management rules and network topology and allocating resources for the service bandwidth application of a user. Signaling is used to deliver, between the bearer network resource managers of each management domain, the request and result of the service bandwidth application of a user, as well as the information of path assigned by each of the bearer network resource managers for the service bandwidth application. When dealing with the service bandwidth application of a user, the bearer control layer determines the path of a user service, and the bearer network resource manager will notify the ER to forward the service flow according to the path determined. Regarding how the bearer network forwards the service flow of the user through a designated route according to the path determined by the bearer control layer, the conventional technology of the industry is mainly based on the Multi-Protocol Label Switching (MPLS) technology to build a Label Switched Path (LSP) along the path of service flow determined by the bearer control layer using the method of resource reservation and build an end-to-end LSP using the explicit routing mechanism of Resource ReSerVation Protocol-Service Traffic Engineering (RSVP-TE) or Constraint-based Label Distribution Protocol (CR-LDP).
At present, key function entities in the network including a separate bearer control layer are simply connected with each other, and if a function entity such as a Resource Control Function (RCF) entity is in failure or is busy in service, other function entities associated with the function entity, such as the ER or a Service Control Function (SCF) entity, cannot operate effectively and fully in the conventional system architecture. That is, in the prior art, there is no reliability technology in the network including a separate bearer control layer for ensuring the normal operation of the network in the case that a function entity is in failure.
At present, the simplest method for ensuring reliability is cold backup. The cold backup means that an entity serves as a complete backup of another entity. Suppose that A is entity A while B is the backup entity of entity A, entity A will be completely replaced by backup entity B if entity A is in failure. However, for backup entity B, the prerequisite for implementing the complete replacement is that both the bearer connection and the service connection have to be rebuilt. Such a method of cold backup, which could be implemented easily, is the most efficient routing mechanism in the early stage of networking because the scale of the network is small, demands of services for real-time characteristics are relatively lower, and the cold backup requires no switching and smoothing. Therefore, the cold backup can usually function well so long as the amount of services is small and an interruption is permitted. However, with the increase in the amount of services and the expansion of the services with a high demand for real-time characteristics, the user hopes to feel as if the services would not be interrupted. As a result, through adopting the cold backup method, the services should be interrupted and rebuilt when a device is in failure. Therefore, if the cold backup is adopted in a Wide Area Network, which is complex and has a high demand for real-time characteristics, many services may be interrupted and rebuilt when there is a failure in a certain segment of the bearer network. At the same time, the method does not have multi-homed characteristics of key service nodes and cannot ensure load balancing and network security.